Wet electrostatic precipitators (ESP) are an old technology originally designed in the 1920's as an acid mist precipitator process using lead collection tubes. The acid mist precipitator uses a water flushing system to remove particles from the collecting surface. The gas stream is either saturated before entering the collection area or the collecting surface is continually wetted to prevent agglomerations. Some aerosols gravitate flow down the collecting surfaces. The acid mist electrostatic precipitator is also effective on oil and tar based condensed aerosols or applications where dry dust particles combine with condensables to form paste like residues. Due to the wet environment, they are typically fabricated out of corrosion resistant materials such as stainless steel.